Experimental and theoretical study of f<inf>T</inf> for SiGe HBTs with a scaled vertical doping profile

Abstract

The high frequency behavior of SiGe HBTs with a vertical doping profile tailored for high transit frequencies f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> was investigated experimentally and theoretically for a series of layout configurations. For f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">t</sub> and f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> best values of 430 GHz and 315 GHz were measured on HBTs with an emitter area of 0.17 × 1.01 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The contribution of device parasitics to the high frequency performance was investigated by means of compact models and device simulation. Measured doping and Ge profiles were used as input for one-dimensional device simulations with a Boltzmann transport equation solver. The results of these simulations were related to the measured characteristics of the actual devices using a compact model which accounts for the external parasitics of the real three-dimensional device.